Peter Ustinov's "Quo Vadis” role (4)
I believe the answer is:
nero
'peter ustinov's quo vadis role' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nero that I've seen before include "Imperial Roman fiddler" , "Fiddling Roman emperor" , "Roman arsonist and fiddler" , "Ancient Roman emperor" , "Emperor said to have fiddled as Rome burned" .)